At the recent Flood Symposium in Calgary the Alberta Government a short list of flood mitigation projects that they would implement over the next three years. The good news for Kananaskis Country is that all of the previously-proposed dry dams have been eliminated, though one new one has been proposed on the Elbow River just above the confluence with McLean Creek. There are three options for reducing flow on the Elbow: the 58 St diversion tunnel, an off-stream diversion reservoir in the Springbank Area and the McLean dry dam. The was some suggestion that only two of these three projects would eventually be built. A decision on this project will be made after the Calgary underground diversion feasibility study is complete. So it may never be built. However, if it’s not built, other works such as dykes or berms will be required to protect Bragg Creek.
The proposed dam is 50 m high, with a storage capacity of 49 million cubic metres. It would require relocation of a portion of Highway 66 and the highway’s bridge over the Elbow River. As you can see from the map below there would be significant changes in the Allen Bill Pond area, with a new start to Elbow/Fullerton trails from a new recreation area. As none of this is likely to happen before 2017, we are going to have to live with temporary trails and trailheads until a decision is made and a master plan for the area trails can be developed.
Alf Skrastins has come up with a different interpretation of the artists rendering that is an improvement on my initial, hurried thoughts. Based on his ideas the area subject to flooding is much larger. Here is a revised map.
There was no indication of the flow level at which the dry dam would be activated. For example, will water start to back up behind the dam if a 2005 level flood was expected? If so, we can expect some flooding upstream every 8-10 years. Is this environmental acceptable?
For more information on dry dams see my previous blog Flood Control Structures Considered for Kananaskis Country.